In recent years, many liquid cooling systems are used to cool electronic equipments. A water cooling system is generally formed of a sealed circulating route, however a refrigerant permeates or evaporates from resin parts or rubber tubes, etc. and air is confirmed to be mixed along with the reduction of the refrigerant. If the accumulated air inside the circulation route mixes in a driving unit, the driving unit runs idle to reduce the flow rate or cause a failure. Then, the cooling efficiency is reduced, thereby possibly leading to insufficient cooling of a heating element and a failure of the apparatus itself. Therefore, in a liquid cooling system, bubbles generated in the system must be trapped before the driving unit and at the same time, a space for storing extra refrigerant (the space hereinafter referred to as a water tank) is required, and it is desirable that air trapped once will not flow into a channel again. Accordingly, water tanks have been suggested, that have the structure to prevent a refrigerant including air mixed therein from flowing out (for example patent documents 1 and 2).
Patent document 1 discloses a method to fix a suction opening of a refrigerant to the center of a water tank so that air will not be mixed in the refrigerant flowing out from the suction opening. With this structure, as long as remaining amount of the refrigerant is half or more of the water tank, the suction opening is always under the liquid level in any direction the corresponding electronic apparatus is used, thus air will not flow out the water tank.
Further, patent document 2 suggests a structure in which a gas accumulated unit is formed in the part except the inner uppermost of the water tank so that air will not be mixed in the refrigerant flowing out of the water tank.
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 2003-78271
[Patent Document 2]
Japanese Unexamined Patent Application Publication No. 2005-285947